Laser SDE effect compensation by adaptive tuning
Laser sub-divisional error (SDE) effect is compensated by using adaptive tuning. This compensated signal can be applied to position detection of stage in ebeam inspection tool, particularly for continuous moving stage.
1. A method for calculating a compensation signal for a sub-divisional error in an object detection, comprising:
obtaining a detected position of the object;
applying a positive gain to a tuning signal;
integrating the tuning signal to a tuned signal;
calculating a deviation between the tuned signal and the detected position;
feeding the deviation to the tuning signal when variations of the tuned signal do not approach to a pre-determined value; and
calculating compensation parameters by using the tuned signal when the variations of the tuned signal approach to the pre-determined value.
2. The method according to claim 1 , wherein when the variations of the tuned signal do not approach to the pre-determined value, another deviation is calculated.
3. The method according to claim 2 , wherein the compensation parameters are fixed when the variation of the tuned signal approach to the pre-determined value.
4. The method according to claim 3 , wherein the detected position of the object detection is obtained by using a laser interferometer and an A/D converter.
5. The method according to claim 3 , wherein the fixed compensation parameters are used in a continuous scanning mode.
6. A method for compensating a sub-divisional error in an object detection, comprising:
obtaining a detected position of the object;
applying a positive gain to a tuning signal;
integrating the tuning signal to a tuned signal;
calculating a deviation between the tuned signal and the detected position;
feeding the deviation to the tuning signal when variations of the tuned signal do not approach to a pre-determined value;
calculating compensation parameters by using the tuned signal when variations of the tuned signal approach to the pre-determined value; and
compensating the sub-divisional error by subtracting the compensation parameters from the sub-divisional error in the object detection.
7. The method according to claim 6 , wherein when the variations of the tuned signal do not approach to the pre-determined value, another deviation is calculated.
8. The method according to claim 7 , wherein the detected position of the object detection is obtained by using a laser interferometer and an A/D converter.
9. The method according to claim 7 , wherein the compensation parameters are fixed when the variation of the tuned signal approach to the pre-determined value.
10. The method according to claim 9 , wherein the fixed compensation parameters are used in a continuous scanning mode.
11. A system for calculating a sub-divisional error in a stage of a charged particle beam inspection tool, comprising:
a parameter generator receiving a detected position and a sub-divisional error frequency, and generating a compensation parameter; and
a signal generator receiving the compensation parameter from the parameter generator and sub-divisional error frequency to generate a compensation signal by using the tuned signal when variations of the tuned signal approach to a pre-determined value.
12. The system according to claim 11 , wherein the parameter generator comprises;
a pair of signal generated units, which generates a pair of tuning signals according to the detected position and the sub-divisional error;
a pair of integrators, integrating the tuning signals and generating two parameters;
a calculation unit, which calculates tuned signals according to the parameters; and
a compensation generator, which calculates compensation parameters by using the tuned signal when variations of the tuned signal approach to a pre-determined value.
13. The method according to claim 12 , wherein when the variations of the tuned signal do not approach to the pre-determined value, another deviation is calculated.
14. The method according to claim 12 , wherein the detected position of the object detection is obtained by using a laser interferometer and an A/D converter.
15. The method according to claim 12 , wherein the compensation parameters are fixed when the variation of the tuned signal approach to the pre-determined value.
16. The method according to claim 15 , wherein the fixed compensation parameters are used in a continuous scanning mode.
17. The method according to claim 16 , wherein the charged particle beam inspection tool is an ebeam inspection tool.